Twist drill



g 10, 1955 B. A. MACKEY 3,199,381

TWIST DRILL Filed March 4, 1963 2 she -s 1 INVENT R. firace d2 777ac%2y Aug. w, 1965 B. A. MACKEY TWIST DRILL 2 Sheets-Sheet 2 Filed March 4, 1963 INVENTOR. Bruce Q 2. macffey (/Qi fy,

3,19,331 TWIST DRILL Bruce A. Mackey, RU. Box 363, Libertyville, Ill. Filed Mar. 4, I953, Ser. No. 262,561 10 Claims. (Cl. 77--7tl) This invention relates in general to drills, and more particularly to improvements in carbide tipped twist drills.

In the past it has been Well known to provide a drill with a hardened point to increase the life of the drill, and to facilitate the passage of the drill through the work. It is also conventional practice to braze a tip of hard material, such as carbide, to the end of the drill to achieve these results. While such expedients have in general served their purpose, they have not proven entirely satisfactory under all conditions of service for the reason that the great amout of heat created when drilling through certain materials has caused the brazed connection of the carbide tip to the drill to break down and the tip to be dislodged. The general purpose of the present invention is therefore to provide a carbide tip twist drill construction which will reduce the amount of heat created by the drilling action, and subsequently reduce the amount of stress imparted to the carbide tip.

An object of the present invention is the provision of a drill which is capable of drilling through different materials having diverse characteristics, such as, wood, cast iron, steel and plastics.

Another object of the present invention is the provision of a twist drill which is capable of drilling a deep hole without binding.

A further object of the invention is the provision of means on the carbide tip to enhance the cutting ability of the drill through the work.

Still another object of the invention is to provide an improved drill which is simple in construction, efiicient in operation, well adapted for its intended purposes, and relatively inexpensive to manufacture and maintain.

These and other objects of the invention will become more fully apparent from the specification and drawing wherein:

FIGURE 1 is a front elevational view of a preferred embodiment of the invention,

FIGURE 2 is a detail view of the carbide tip used in the embodiment illustrated in FIGURE 1 prior to sharpening,

FIGURE 3 is a top view of the tip illustrated in FIG- URE 2,

FIGURE 4 is a sectional view taken along line 44 of FIGURE 2 showing the tip in a sharpened condition,

FIGURE 5 is a sectional view taken along line 55 of FIGURE 2 showing the tip in a sharpened condition,

FIGURE 6 is a front elevational view of a second embodiment of the carbide tip,

FIGURE 7 is a sectional view taken along line 7--7 of FIGURE 6,

FIGURE 8 is a sectional view taken along line 88 of FIGURE 6,

FIGURE 9 is a front elevational view of a third embodiment of the carbide tip, and

FIGURE 10 is a view taken along line 10--10 of FIG- URE 9.

Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views, reference numeral 10 is used in FIGURE 1 to indicate the preferred embodiment of the twist drill in its entirety. Twist drill 10 comprises an elongated shank 11 terminating in a stub portion 12, which is adapted to be gripped in a suitable chucking means, not shown.

Shank I1 is provided with a spiral groove 13 which extends axially along the shank substantially from one end nited States Patent C) of the drill to the other. Shank 11 is preferably plated with a hard material, such as chrome or the like, to provide a smooth surface which facilitates passage of the drilled work particles along groove 13. Groove 13 is cut deeply into the sides of shank 11 to allow particles of relatively large size to pass along the groove. Because of the depth of the groove 13, the mouth of the groove is exceptionally wide and the number of revolutions which the groove makes around the shank is materially reduced. This shortens the path which the out work particles must travel from the cutting edge of the drill to their point of emergence at the opposite end of the drill. These features cooperate to provide a drill which will cut through the work without packing of the out work particles and therefore without binding. It is obvious that such a drill will cut a deep hole in the work without excessive heating, and will substantially eliminate the necessity of removing the drill from the hole to discharge the accumulated work particles from the drill flutes. It should also be noted when drilling a shallow hole the problem of excessive heating is not present, and the drill may be provided with a smooth cylindrically shaped shank, which eliminates the necessity of providing grooves 13.

A cutting tip 14, formedof an exceptionally hard material such as carbide, ceramic or the like, is affixed to the forward end of the drill as by brazing, welding or the equivalent fastening means. Tip 14 is provided with a pair of cutting edges 15 and is which taper forwardly to a point 17. Tip 14 further includes a pair of side edges 18 and 19 which taper rearwardly from their junction with cutting edges 15 and 16 to form a base 20 of reduced width. The provision of tapered side edges is important in that it reduces the amount of the tip which contacts the wall of the hole being drilled. This eliminates the scraping of the side edges upon the wall of the hole being drilled, which is prevalent in known devices having side edges which are parallel to the axis of the drill. The elimination of the frictional engagement of the tip side edges with the walls of the hole being drilled materially reduces the amount of heat created by the drilling action, and thus obviates the possibility of the tip becoming unbonded from the drill shank.

Grooves 21 and 22 are provided in opposite faces of tip 14 adjacent to and parallel with cutting edges 15 and 16, respectively. Grooves 21 and 22 are positioned in the leading faces of tip 14, when the drill is rotated clockwise as viewed in FIGURE 1, and form, in combination, means for cutting the work from the bottom of the hole being drilled. This enhanced cutting action is extremely important when drilling hard to drill materials, such as cast iron or some plastics, in that it reduces the possibility of the drill breaking during the drilling action, since a minimum amount of power is required in cutting, and the chips are broken up in small chunks so as to pass out the hole being drilled without packing or binding. Surfaces 23 and 24 are ground so as to be positioned at an acute angle with respect to the faces of tip 14 to produce a sharpened positive cutting edge.

Referring now to FIGURES 68, another embodiment is shown which has particular utility when drilling hard materials, such as, stainless steel or tool steel. In this embodiment the tip 25 has the same configuration as the embodiment shown in FIGURES 1-5, that is, side edges 26 and 27 taper rearwardly from their junction with cutting edges 28 and 29 to form a base 30 of reduced width, and surfaces 30 and 31 are ground so as to be positioned at an angle with respect to the faces of the tip. However, it will be noted that the grooves 32 and 33, which are adjacent to and parallel with edges 28 and 29, do not extend the entire length of the cutting edges, and thus define a central ungrooved portion 34 of uniform thickness adjacent point 35. The presence of a Z solid ungrooved portion 34- prevents the accumulation of fine chips and particles in the grooves adjacent point 34, and thus reduces the pressure buildup at the point and materially strengthens the tip.

The tip embodiment illustrated in FIGURES 9 and is substantially identical to that shown in FIGURES 6-8 except that the solid portion 34 is extended outwardly ahead of cutting edges 28 and 29. This enables a small pilot hole to be out ahead of the main hole being drilled, which stabilizes the drill to a large extent, and allows the drill to cut without tearing and without chaering.

Thus it can be readily understood that what has been provided is an improved twist drill which can effectively cut through many different materials having diverse characteristics in an efiicient manner, and with a materially reduced possibility of failure. It should also be understood that the invention has been illustrated in a preferred form only and improvements and modifications may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

What is claimed is:

f. A drill comprising: an elongate shank having a longitudinal axis; a cutting tip afiixed to the forward end of said shank; said cutting tip htving generally parallel front and rear faces with side faces disposed transversely with respect to said front and rear faces, said side faces tapering generally uniformly rearwardly at an acute angle with respect to the axis of said shank to define a cutting tip base of reduced width at the rearward end of said cutting tip; and cutting tip including cutting faces at the forward end thereof, each of said cutting faces tapering forwardly from the forwardmost end of one of said side faces, and converging toward one another to define a leading cutting tip point; one of said cutting faces being disposed at an acute angle with respect to said cutting tip front face to define a cutting edge at the forwardmost portion of the cutting tip front face, and the other cutting face being disposed at an acute angle with respect to said cutting tip rear face to define a cutting edge at the forwardmost portion of the cutting tip rear face.

2. A drill as defined in claim it in which said shank has a substantially cylindrical outer periphery, and wherein a spiral groove is provided in said shank extending longitudinally therealong.

3. The invention set forth in claim 1 wherein said tip is formed of a carbide material.

4. A drill as defined in claim It wherein a groove is provided in each of the front and rear faces of the cutting tip adjacent to and parallel their respective cutting edges.

5. A drill as defined in claim 4 wherein said grooves are immediately adjacent their respective cutting edges, so that said cutting edges overlie their respective grooves and form Wall means defining one side of the groove.

6. The invention set forth in claim 4 wherein said grooves are substantially coextensive with said cutting edges.

'7. The invention set forth in claim 4 wherein said grooves terminate short of said point to define a solid ungrooved portion adjacent said point.

2%. The invention set forth in claim 7 wherein said solid ungrooved portion extends forwardly from said cutting edges.

9. A drill comprising: an elongate generally cylindrical shank having a longitudinal axis, said shank having a relatively wide spiral groove therein extending longitudinally therealong; a hardened cutting tip affixed to the forward end of said shank; said cutting tip having generaily parallel front and rear faces with side faces disposed transversely with respect to said front and rear faces, said side faces tapering generally uniformly rearwardiy at an acute angle with respect to the axis of said shank to define a cutting tip base of reduced width at the rearward end of said cutting tip, said angle being sufficiently large so that only the forwardrnost portions of said side faces contact the side wall of a hole being drilled; said cutting tip including cutting faces at the forward end thereof, each of said cutting faces tapering forwardly from the foiwvardrnost end of one of said side faces, and converging toward one another to define a leading cutting tip point; one of said cutting faces being disposed at an acute angle with respect to said cutting tip front face to define a cutting edge at the forwardmost portion of the cutting tip front face, and the other cuting face being disposed at an acute angle with respect to said cutting tip rear face to define a cutting edge at the forwardmost portion of the cutting tip rear face; and an arcuate groove in said front and rear faces immediate- 1y adjacent and parallel with the cutting edge thereon. id. A cutting tip for use in a drill comprising: a cutting tip body adapted to rotate about a longitudinal axis and having generally parallel front and rear faces with sides faces disposed transversely with respect to said front and rear faces, said side faces tapering generally uniformly rearwardly at an acute angle with respect to said axis to define a cutting tip base of reduced width at the rearwardend of said cutting tip, said angle being sufficienly large so that only the forwardmost portions of said side faces contact the side wall of a hole being drilled; said cutting tip body including cutting faces at the forward end thereof, each of said cutting faces tapering forwardly from the forwardinost end of one of said side faces, and converging toward one another to define aleading cutting tip point; one of said cutting faces being disposed at an acute angle with respect to the front face of said cutting tip body to define a cutting edge at the forwardmost portion or" the cutting tip front face and the other cutting face being disposed atan acute angle with respect to the rear face of said cutting tip body to define a cutting edge at the forwardrnost portion of the cutting tip rear face; and an arcuate groove in said front and rear faces immediately adjacent and parallel with the cutting edge thereon.

References titted by the Examiner UNITED STATES PATENTS 3,099,174 7/63 Cogsdill 77-73.5 3,117,637 1/ 64 Mortensen 77-70 XR FOREIGN PATENTS 550,306 1/43 Great Britain.

W ELLIAM W. DYER, IR., Primary Examiner.

l. SPENCER OVERHOLSER, ANDREW R. JUHASZ,

am ners. 

1. A DRILL COMPRISING: AN ELONGATE SHANK HAVING A LONGITUDINAL AXIS; A CUTTING TIP AFFIXED TO THE FORWARD END OF SAID SHANK; SAID CUTTING TIP HAVING GENERALLY PARALLEL FRONT AND REAR FACES WITH SIDE FACES DISPOSED TRANSVERSELY WITH RESPECT TO SAID FRONT AND REAR FACES, SAID SIDE FACES TAPERING GENERALLY UNIFORMLY REARWARDLY AT AN ACUTE ANGLE WITH RESPECT TO THE AXIS OF SAIAD SHANK TO DEFINE A CUTTING TIP BASE OF REDUCED WIDTH AT THE REARWARD END OF SAID CUTTING TIP; AND CUTTING TIP INCLUDING CUTTING FACES AT THE FORWARD END THEREOF, EACH OF SAID CUTTING FACES TAPERING FORWARDLY FROM THE FORWARDMOST END OF ONE OF SAID SIDE FACES, AND CONVERGING TOWARD ONE ANOTHER TO DEFINE A LEADING CUTTING TIP POINT; ONE OF SAID CUTTING FACES BEING DISPOSED AT AN ACUTE ANGLE WITH RESPECT TO SAID CUTTING TIP FRONT FACE TO DEFINE A CUTTING EDGE AT THE FORWARDMOST PORTION OF THE CUTTING TIP FRONT FACE, AND THE OTHER CUTTING 